Tweak editor select mode drag threshold for better usability

- Use a smaller drag threshold (8 pixels instead of 10 pixels).
- Scale the 2D editor drag threshold with the zoom to make it
  work the same regardless of the current zoom level.

editor/plugins/canvas_item_editor_plugin.cpp

@@ -2324,7 +2324,7 @@ bool CanvasItemEditor::_gui_input_select(const Ref<InputEvent> &p_event) {
 		}
 		if (m.is_valid()) {
 			Point2 click = transform.affine_inverse().xform(m->get_position());
-			bool movement_threshold_passed = drag_start_origin.distance_to(click) > 10 * EDSCALE;
+			bool movement_threshold_passed = drag_start_origin.distance_to(click) > (8 * MAX(1, EDSCALE)) / zoom;
 			if (m.is_valid() && movement_threshold_passed) {
 				List<CanvasItem *> selection2 = _get_edited_canvas_items();
 

editor/plugins/node_3d_editor_plugin.cpp

@@ -1467,7 +1467,7 @@ void Node3DEditorViewport::_sinput(const Ref<InputEvent> &p_event) {
 			} else if (nav_scheme == NAVIGATION_MODO && m->is_alt_pressed()) {
 				nav_mode = NAVIGATION_ORBIT;
 			} else {
-				bool movement_threshold_passed = _edit.original_mouse_pos.distance_to(_edit.mouse_pos) > 10 * EDSCALE;
+				const bool movement_threshold_passed = _edit.original_mouse_pos.distance_to(_edit.mouse_pos) > 8 * EDSCALE;
 				if (clicked.is_valid() && movement_threshold_passed) {
 					if (!clicked_includes_current) {
 						_select_clicked(clicked_wants_append, true);